1. Field of the Invention
The present invention relates generally to methods, devices and systems for transcutaneous inductive power links, and more specifically, to varying the effective coil area for an inductive transcutaneous power link.
2. Related Art
Medical devices having one or more implantable components, generally referred to as implantable medical devices, have provided a wide range of therapeutic benefits to patients over recent decades. In particular, devices such as hearing aids, implantable pacemakers, defibrillators, functional electrical stimulation devices, such as cochlear prostheses, organ assist or replacement devices, and other partially or completely-implanted medical devices, have been successful in performing life saving and/or lifestyle enhancement functions for a number of years.
The type and function of implantable medical devices has increased over the years. For example, many such implantable medical devices often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical, electrical or electronic components that are permanently or temporarily implanted in a patient. Such medical devices may be used to perform diagnosis, prevention, monitoring, treatment or management of a disease or injury or symptom thereof, or to investigate, replace or modify of the anatomy or of a physiological process. Many implantable components receive power and/or data from external components that are part of, or operate in conjunction with, the implantable component. For example, some implantable medical devices include a power source integrated into the implantable component.
A cochlear prosthesis is a specific type of hearing prostheses that delivers electrical stimulation to the recipient's cochlea. As used herein, cochlear implants also include hearing prostheses that deliver electrical stimulation in combination with other types of stimulation, such as acoustic or mechanical stimulation.
Implantable medical devices, including cochlear implants, sometimes rely on an inductive link in order to transfer power to an implanted power consuming device. In an active implantable system such as a cochlear implant having an external coil and an implanted coil, the power transfer between the coils is based on magnetic induction between the coils.